Semiconductor device and fabrication method thereof

ABSTRACT

A semiconductor device superior in reliability and suitable for microminiaturization is provided. An organic SOG film is formed on a silicon oxide film. Boron ions are implanted into the organic SOG film. By introducing boron ions into the organic SOG film, the organic components in the film are decomposed. Also, the moisture and hydroxyl group included in the film are reduced. After a metal interconnection is embedded in a modified SOG film by the Damascene method, a modified SOG film is formed thereon. Then, contact holes are formed. After a contact hole interconnection is embedded in the contact holes, a modified SOG film and an upper metal interconnection are formed by the Damascene method.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a semiconductor device and amethod of fabricating the same.

[0003] 2. Description of the Background Art

[0004] In the past several years, intensive efforts have been taken toreduce the size of interconnections and provide multilayers for thepurpose of further increasing the integration density of semiconductorintegrated circuit devices. An interlayer insulation film is providedbetween each interconnection to obtain a multilayer structure of theinterconnection. If the surface of this interlayer insulation film isnot planar, a step-graded portion will be generated at theinterconnection formed above the interlayer insulation film. This willcause defects such as disconnection. Therefore, the surface of theinterlayer insulation film (the surface of the device) must be made asflat as possible. The technique to planarize the surface of the deviceis called planarization. This planarization technique has become everimportant in reducing the size and providing multilayers of theinterconnection.

[0005] In planarization, an SOG (Spin-On-Glass) film is known as aninterlayer insulation film that is generally used. Recently, developmentin the planarization technique taking advantage of the flow of theinterlayer insulation film material is particularly noticeable.

[0006] An “SOG” is the generic term of a film mainly composed of asolution in which a silicon compound is dissolved in an organic solvent,and silicon dioxide formed from that solution.

[0007] In forming an SOG film, first a solution having a siliconcompound dissolved in an organic solvent is applied in droplets on arotated substrate. By this rotation, the solution coating is provided soas to alleviate the step-graded portion on the substrate correspondingto the interconnection. More specifically, the coating is formed thickat the concave portion and thin at the convex portion on the substrate.As a result, the surface of the solution coating is planarized.

[0008] Then, heat treatment is applied to vaporize the organic solvent.Also, polymerization proceeds to result in a planarized SOG film at thesurface.

[0009] An SOG film is typically classified into an inorganic SOG filmthat does not include any organic component in a silicon compound, asrepresented by the following general formula (1), and an organic SOGfilm including an organic component in a silicon compound, asrepresented by the following general formula (2).

[SiO₂]_(n)  (1)

[R_(x)Si_(Y)O_(Z)]_(n)  (2)

[0010] (n, X, Y, Z: integer; R: alkyl group or aryl group)

[0011] Inorganic and organic SOG films have superior flatness. However,the inorganic SOG film includes a great amount of moisture and hydroxylgroup. Therefore, it may adversely affect the metal interconnection andthe like. There is the possibility of inducing problems such asdegradation in electrical characteristics as well as corrosion. Asimilar, though less susceptible, problem is seen in an organic SOGfilm. This is because the organic SOG film includes some amount ofmoisture and hydroxyl group.

[0012] To compensate for this disadvantage when an SOG film is employedas an interlayer insulation film, an insulation film such as a siliconoxide film formed by, for example, plasma CVD, having thecharacteristics of insulation and mechanical strength in addition to theproperty of blocking moisture and hydroxyl group is provided between theSOG film and the metal interconnection (refer to Japanese PatentLaying-Open No. 5-226334, for example).

[0013] The provision of an insulation film such as a silicon oxide filmformed by plasma CVD as in the conventional case between an SOG film anda metal interconnection will limit the decrease between the patterns ofthe underlying metal interconnection to bar the microminiaturization ofthe elements.

SUMMARY OF THE INVENTION

[0014] An object of the present invention is to provide a semiconductordevice of superior reliability and suitable for microminiaturization,and a method of fabricating such a semiconductor device.

[0015] A method of fabricating a semiconductor device according to thepresent invention includes the steps of forming a first insulation filmon a substrate, introducing impurities into the first insulation film,and embedding and forming a first conductive layer in the firstinsulation film. In a preferable embodiment, the step of forming a firstconductive layer includes the step of embedding the first conductivelayer in the first insulation film so that the surface of the firstconductive layer is exposed. The method of this preferable embodimentfurther includes the steps of forming a second insulation film on thefirst insulation film, forming a contact hole in the second insulationfilm to expose a portion of the first conductive layer, and forming asecond conductive layer in the contact hole, electrically connected tothe first conductive layer. This method further desirably includes thestep of introducing impurities into the second insulation film.

[0016] Another method of a preferable embodiment includes, afterformation of the second insulation film and before formation of thecontact hole, the steps of forming a first mask pattern on the secondinsulation film, forming a third insulation film on the secondinsulation film and on the first mask pattern, forming a second maskpattern having an opening larger than the first mask pattern on thethird insulation film, etching the third insulation film using thesecond mask pattern to form a trench in the third insulation filmarriving at the first mask pattern. In this method, the step of forminga contact hole includes the step of etching the second insulation filmusing the first mask pattern, and the step of forming a secondconductive layer includes the step of forming a third conductive layerelectrically connected to the second conductive layer in the trench, inaddition to the formation of the second conductive layer.

[0017] Preferably, this method further includes the step of introducingimpurities into the third insulation film.

[0018] A further method of a preferable embodiment further includes thestep of forming a fourth insulation film on the substrate, prior toformation of the first insulation film. In this method, the step ofintroducing impurities into the first insulation film is carried outunder the condition where the impurities arrive at the interface betweenthe first insulation film and the fourth insulation film.

[0019] Preferably, the first insulation film includes a silicon oxidefilm containing at least 1% of carbon. Also preferably, the secondinsulation film includes a silicon oxide film containing at least 1% ofcarbon. Also preferably, the third insulation film includes a siliconoxide film containing at least 1% of carbon. Also preferably, the firstinsulation film includes an inorganic SOG film.

[0020] A still another method of a preferable embodiment includes, afterformation of the second insulation film and before formation of acontact hole, the steps of forming a third mask pattern on the secondinsulation film, etching the second insulating film using the third maskpattern to selectively reduce the thickness of the second insulationfilm, and forming a fourth mask pattern on the second insulation film soas to expose a portion of the region reduced in thickness. In thismethod, the method of forming a contact hole includes the step ofetching the second insulation film using the fourth mask pattern. Thestep of forming the second conductive layer includes the step of forminga third conductive layer electrically connected to the second conductivelayer on the region that is reduced in thickness, in addition to theformation of the second conductive layer.

[0021] Yet a further method of a preferable embodiment includes thesteps of forming a second insulation film on the first insulation film,forming a fifth mask pattern on the second insulation film, etching thesecond insulation film using the fifth mask pattern to form a contacthole in the second insulation film so as to expose a portion of thefirst conductive layer, forming a resist film in the contact hole and onthe second insulation film after the fifth mask pattern is removed,patterning the resist film on the second insulation film to form a sixthmask pattern on the contact hole having an opening larger than thecontact hole, etching the second insulation film using the sixth maskpattern to selectively reduce the thickness of the second insulationfilm, removing the resist pattern remaining in the contact hole and thesixth mask pattern, and forming a second conductive layer electricallyconnected to the first conductive layer in the contact hole.

[0022] In a preferable embodiment, the method further includes the stepof introducing impurities into the second insulation film prior toformation of the contact hole in the second insulation film.

[0023] By introducing impurities into the first insulation film, thesecond insulation film and the third insulation film, respective filmsare modified in nature so that the moisture and hydroxyl group includedin the films are reduced. Also, the film becomes less hygroscopic.Accordingly, the insulative property of the insulation film can beimproved.

[0024] Particularly, by introducing impurities into the first, second,and third insulation films prior to formation of the firstinterconnection (conductive layer), the second interconnection(conductive layer) and the third interconnection (conductive layer),respectively, the impurities can be implanted to a depth substantiallyuniform over the entire film. Respective films can be modifieduniformly.

[0025] By forming a fourth insulation film under the first insulationfilm in advance and introducing impurities into the first insulationfilm under the condition where the impurities reach the interfacebetween the first and fourth insulation films, the intensity ofadherence between the first insulation film and the fourth insulationfilm can be improved.

[0026] A semiconductor device according to the present inventionincludes a first conductive layer having a top face on a first plane, afirst insulation layer introduced with impurities and having a top faceon a second plane parallel to the first plane, a second insulation layerintroduced with impurities and having a top face on a third planeparallel to the second plane, a second conductive layer embedded in thefirst insulation layer, and having a bottom in contact with the top faceof the first conductive layer and a top face located on the secondplane, and a third conductive layer embedded in the second insulationfilm, having a bottom in contact with the top face of the secondconductive layer, and a top face located on the third plane.

[0027] In one embodiment, the second conductive layer and the thirdconductive layer are a single layer formed continuously.

[0028] In another embodiment, the first insulation layer and the secondinsulation layer are a single layer formed continuously. The secondconductive layer and the third conductive layer are a single layerformed continuously.

[0029] Preferably, each of the first and second insulation layersincludes an SOG film into which impurities are introduced by ionimplantation.

[0030] In one embodiment, each of the first and second insulation layersincludes a silicon nitride film on an SOG film.

[0031] In a preferable embodiment, a first conductive layer is embeddedin a planarized insulation layer. Preferably, the insulation layerincludes an SOG film into which impurities are introduced by ionimplantation.

[0032] The foregoing and other objects, features, aspects and advantagesof the present invention will become more apparent from the followingdetailed description of the present invention when taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIGS. 1-9 are schematic sectional views of a semiconductor deviceaccording to a first embodiment of the present invention indicatingfabrication steps thereof.

[0034]FIG. 10 is a diagram of characteristics for describing anembodiment of the present invention, indicating the relationship betweencumulative frequency and adherence intensity.

[0035]FIG. 11 is a diagram of characteristics for describing anembodiment of the present invention, indicating the relationship betweenthe processing condition and film thickness.

[0036]FIG. 12 is a diagram of characteristics for describing anembodiment of the present invention, indicating the relationship betweentemperature and intensity.

[0037] FIGS. 13-14 are diagrams of characteristics for describing anembodiment of the present invention, indicating the relationship betweentime and the O—H area.

[0038] FIGS. 15-20 are schematic sectional views of a semiconductordevice according to a second embodiment of the present inventionindicating fabrication steps thereof.

[0039] FIGS. 21-26 are schematic sectional views of a semiconductordevice according to a third embodiment of the present inventionindicating fabrication steps thereof.

[0040] FIGS. 27-33 are schematic sectional views of a semiconductordevice according to a fourth embodiment of the present inventionindicating fabrication steps thereof.

[0041] FIGS. 34-39 are schematic sectional views of a semiconductordevice according to a fifth embodiment of the present inventionindicating fabrication steps thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] First Embodiment

[0043] A method of fabricating a semiconductor device according to afirst embodiment of the present invention will be described hereinafterwith reference to FIGS. 1-9.

[0044] In the first step (refer to FIG. 1), a silicon oxide film 2 (filmthickness: 200 nm) is formed on a (100) p type (or n type) singlecrystal silicon substrate 1. An organic SOG film 3 is formed on siliconoxide film 2. Organic SOG film 3 has the composition of[(CH₃)₂Si₄O₇]_(n) and a film thickness of 600 nm. Silicon oxide film 2corresponds to the fourth insulation film of the present invention.Organic SOG film 3 corresponds to the first insulation film of thepresent invention.

[0045] Silicon oxide film 2 is formed by plasma CVD. As the reactiongas, monosilane and nitrous oxide (SiH₄+N₂O), monosilane and oxygen(SiH₄+O₂), TEOS (Tetra-ethoxy-silane) and oxygen (TEOS+O₂) and the likeare used. The temperature of film growth is 300-900° C.

[0046] Silicon oxide film 2 can be formed by a method other than plasmaCVD (atmospheric pressure CVD, low pressure CVD, ECR plasma CVD, photoexcitation CVD, TEOS-CVD, PVD, etc.). For example, the gas used inatmospheric pressure CVD is monosilane and oxygen (SiH₄+O₂), and thetemperature of film growth is not more than 400° C. The gas used inreduced pressure CVD is monosilane and nitrous oxide (SiH₄+N₂O). Thetemperature of film growth is not more than 900° C.

[0047] The method of forming organic SOG film 3 is set forth in thefollowing. First, an alcohol based solution of a silicon compound of theabove composition (for example, IPA+Acetone) is applied on a substrate 1in droplets that is rotated for 20 seconds at the rotational speed of2300 rpm. Thus, a coating of the alcohol based solution is provided onsubstrate 1. Here, the alcohol based solution coating is formed thick atthe concave portion and thin at the convex portion with respect to thestep-graded portion on substrate 1 to alleviate the unevenness. As aresult, the surface of the alcohol based solution coating is madeplanar.

[0048] Then, heat treatment of 100° C. for 1 minute, 200° C. for 1minute, 300° C. for 1 minute, 22° C. for 1 minute, and 430° C. for 30minutes are sequentially carried out in an atmosphere of nitrogen,whereby the alcohol based solution is vaporized and polymerizationproceeds. An organic SOG film of approximately 300 nm in thickness witha flat surface is formed. By repeating the process of forming a coatingto the heat treatment one more time, an organic SOG film 3 of 600 nm inthickness is obtained.

[0049] Since the underlying face is planer, this organic SOG film 3 isapplied at substantially uniform thickness over the entire plane of thesubstrate. Organic SOG film 3 is a silicon oxide film containing atleast 1% of carbon.

[0050] At the second step (refer to FIG. 2), boron ions (B⁺) are dopedinto organic SOG film 3 under the condition of an acceleration energy of140 KeV and dose of 2×10¹⁵ atoms/cm². By implanting ions under such acondition, boron ions arrive at the interface between organic SOG film 3and silicon film 2.

[0051] By introducing boron ions into organic SOG film 3 in theabove-described manner, the organic component in the film is decomposed.The moisture and hydroxyl group included in the film are reduced.Furthermore, the intensity of adherence between organic SOG film 3 andsilicon oxide film 2 is improved by introducing the boron ions to theinterface. As a result, organic SOG film 3 is modified to a SOG film 4(referred to as “modified SOG film” hereinafter) with no organiccomponent and with little moisture and hydroxyl group, and having highadhesion with the underlying film (silicon oxide film 2). Since organicSOG film 3 is substantially uniform in film thickness over the entireface of the substrate, the entire organic SOG film 3 is modifieduniformly. Also, the adhesion with the underlying film is improved overthe entire face. It is to be noted that this modified SOG film 4 is asilicon oxide film containing at least 1% of carbon.

[0052] At the third step (refer to FIG. 3), anisotropic etching iscarried out with a resist pattern (not shown) as a mask and using afluoro carbon type gas as the etching gas to form a trench 5 in modifiedSOG film 4.

[0053] At the fourth step (refer to FIG. 4), the interior of trench 5 iscleaned by sputter etching using inert gas (for example, Ar). Then, aTiN film functioning as an adhesion layer and barrier layer is formedusing magnetron sputtering or CVD within trench 5 and on modified SOGfilm 4. Then, a Cu film is formed thereon by CVD or plating. The surfaceof the Cu film is polished by CMP (Chemical Mechanical Polishing). Ametal interconnection 6 formed of TiN and Cu is embedded in trench 5.This technique of embedding a metal interconnection is generallyreferred to as the Damascene method.

[0054] By virtue of the superior coverage of the organic SOG film, theorganic SOG can be filled sufficiently between metal interconnections 6even if organic SOG film 3 is applied after forming the pattern of metalinterconnection 6 in the first to fourth steps, for example. However,when an organic SOG film is applied on an uneven surface such as theunderlying interconnection pattern, the film thickness of organic SOGfilm 3 may vary depending on whether there is an interconnectionthereunder or not. If ion implantation is carried out to modify theorganic SOG film in such a state, the lower layer portion of the organicSOG film will include a portion that is modified and a portion that isnot modified. This will induce various problems that will be describedafterwards.

[0055] In the present embodiment, organic SOG film 3 is formed on a flatunderlying face prior to formation of metal interconnection 6.Therefore, the film thickness of organic SOG film 3 is substantiallyuniform. The entire organic SOG film 3 is modified substantiallyuniformly.

[0056] At the fifth step (refer to FIG. 5), an organic SOG film 7 of 600nm in film thickness is formed on modified SOG film 4 and metalinterconnection 6. The composition and fabrication method of organic SOGfilm 7 are similar to those of the above-described organic SOG film 3.Organic SOG film 7 corresponds to the second insulation film of thepresent invention.

[0057] At the sixth step (refer to FIG. 6), boron ions are doped intoorganic SOG film 7 under the condition of an acceleration energy of 140KeV and dose of 2×10¹⁵ atoms/cm²,whereby organic SOG film 7 is modified(referred to as modified SOG film 8 hereinafter), similar to modifiedSOG film 4. Ion implantation at such a condition allows the boron ionsto arrive at the interface between organic SOG film 7 and modified SOGfilm 4.

[0058] Since organic SOG film 7 is substantially uniform in filmthickness over the entire face of the substrate, the entire organic SOGfilm 7 is modified substantially uniformly.

[0059] At the seventh step (refer to FIG. 7), anisotropic etching iscarried out with a resist pattern (not shown) as a mask, using a fluorocarbon type gas as the etching gas, whereby contact holes 9 a, 9 bcommunicating with metal interconnection 6 are formed in modified SOGfilm 8. Here, contact error will not occur even when a contact hole isformed deviated from the top face of metal interconnection 6, such ascontact hole 9 b, due to mask misalignment.

[0060] In the case where there is a portion not modified in the film(particularly, the lower layer portion) due to insufficient ionimplantation into organic SOG film 3 and a contact hole is formed indeviation in that non-modified portion, that non-modified portion mayshrink during the oxygen plasma ashing process carried out to remove thephoto resist used as an etching mask in the contact hole formation step.As a result, a recess will be generated in the hole. There is apossibility of contact error caused by insufficient embedding of theconnection hole interconnection in the hole.

[0061] If a non-modified portion of the organic SOG film is exposed inthe contact hole, H₂O and CH₃ will desorb from the organic SOG when Cuis to be formed by CVD in the contact hole. The source gas to form Cuwill not be able to enter the contact hole sufficiently. There is apossibility that the Cu of an improper shape will be formed within thecontact hole.

[0062] In the present embodiment, the entire organic SOG film 3 ismodified substantially uniformly as described above. Only a modifiedportion will be exposed if the contact hole is formed in deviation.

[0063] At the eighth step (refer to FIG. 8), the interior of contactholes 9 a and 9 b are cleaned by sputter etching using inert gas (forexample Ar). Then, a TiN film serving as an adhesion layer and a barrierlayer is formed on modified SOG film 8 including contact holes 9 a and 9b by magnetron sputtering or CVD. A Cu film is formed thereon by CVD orplating. Then, the surface of the Cu film is polished by CMP. Finally, aconnection hole interconnection 10 formed of TiN and Cu is embedded incontact holes 9 a and 9 b.

[0064] At the ninth step (refer to FIG. 9), the oxide film and the likeat the surface of connection hole interconnection 10 are removed, asnecessary by sputter etching using inert gas (for example Ar).

[0065] Then, on modified SOG film 8 and connection hole interconnection10, a modified SOG film 11 and an upper metal interconnection 12 (amulti layer of TiN and Cu) embedded in modified SOG film 11 andelectrically connected with connection hole interconnection 10 areformed, similar to the previous first to fourth steps.

[0066] Since boron ions are introduced to the interface between organicSOG film 3 and silicon oxide film 2 as described above in the ionimplantation process, modified SOG film 4 is less easily peeled off fromsilicon oxide film 2.

[0067] Table 1 shows the verified results using a tensile tester of theadhesion intensity between an SOG film and a silicon oxide film for atest device having an SOG film (film thickness 600 nm) formed on asilicon oxide film. Four types of SOG films were provided as shown inTable 1. Ten samples were provided for each type. The film peel off ratewas determined by carrying out a tension test at the tensile force of500 Kg/cm² to observe how many of the samples exhibited peel off. TABLE1 Condition Film Peel Off Rate Organic SOG film 100% Low-pressure OxygenPlasma Treatment 100% Modified SOG film (Ar Ion Implantation)  0%Modified SOG film (B Ion Implantation)  0%

[0068] The condition column in Table 1 corresponds to those used as anSOG film. The low-pressure oxygen plasma process implies that an organicSOG film is exposed to oxygen plasma. The modified SOG film is formedunder the conditions identical to those of the present embodiment. It isappreciated that, by employing a modified SOG film as the SOG film, theadhesion with the underlying silicon oxide film is improved to preventthe film from peeling off.

[0069]FIG. 10 shows the adherence intensity when boron (B⁺) ions areimplanted under different conditions to the SOG film in the test devicesimilar to that of Table 1. The dose was set to a constant value of1+10¹⁵ atoms/cm². The acceleration energy was varied to 20, 60, 100 and140 KeV. The label “UNIMPLANTED” in the drawing implies that the film isnot subjected to ion implantation, i.e., an organic SOG film.

[0070] Those not subjected to ion implantation have low adherenceintensity between the SOG film and the silicon oxide film to be easilypeeled off. Those subjected to ion implantation have a higher adherenceintensity as the acceleration energy is increased. Particularly, anadherence intensity exceeding 700 Kgf/cm² can be obtained when theacceleration energy is 60 KeV or above. This improvement in adhesioncould be attributed to the arrival of the ions at the interface betweenthe SOG film and the silicon oxide film to cause mixing andrecombination of the elements at the interface.

[0071] Modified SOG films 4, 8 and 11 hardly shrink during the oxygenplasma ashing process carried out to remove the photo resist used as theetching mask. No recess will be generated in the formation of trench 5and contact holes 9 a and 9 b. It is therefore possible to embed metalinterconnection 6 and connection hole interconnection 10 sufficiently intrench 5 and contact holes 9 a and 9 b.

[0072] The modified SOG film is also superior in oxygen plasmaresistance. FIG. 11 shows, as an index of oxygen plasma resistance,change in the film thickness when the modified SOG film formed byimplanting argon (Ar) ions into the organic SOG film is exposed tooxygen plasma for the evaluation of reduction in the film thickness ofthe modified SOG film. Ions were implanted under the condition of anacceleration energy of 140 KeV and dose of 1×10¹⁵ atoms/cm².

[0073] When the organic SOG film was subjected to oxygen plasma (oxygenplasma process), the film thickness was reduced 16% than the initialfilm thickness of the organic SOG film (untreated). When the modifiedSOG film was subjected to oxygen plasma (oxygen plasma process after Arion implantation) there was almost no reduction in the film thicknesscompared to that of the initial modified SOG film (Ar ion implantation).However, the film thickness of the modified SOG film is reduced 25% incomparison to that of the organic SOG film.

[0074] From the above results, it is appreciated that the modified SOGfilm is superior in oxygen plasma resistance.

[0075]FIG. 12 shows the results of evaluation using the TDS method(Themal Desorption Spectroscopy) applying heat treatment for 30 minutesin an atmosphere of nitrogen to an organic SOG film (unimplanted) and amodified SOG film (Ar ion implantation). The ions were implanted underthe conditions of an acceleration energy of 140 KeV and a dose of 1×10¹⁵atoms/cm².

[0076] The chart represents the amount of desorption as to H₂O (m/e=18).It is appreciated from FIG. 12 that the modified SOG film exhibitslittle desorption as to H₂O (m/e=18). This means that the moisture andhydroxyl group included in the organic SOG film are reduced byimplanting ions to the organic SOG film to obtain a modified SOG film.

[0077]FIG. 13 shows the evaluation result of the moisture in the filmsof an organic SOG film (untreated), an organic SOG film subjected tooxygen plasma (oxygen plasma process), and a modified SOG film (Ar ionimplantation) left in the atmosphere of a clean room to observe thehygroscopicity of an organic SOG film and a modified SOG film. Theamount of moisture in each film was indicated by the integratedintensity of the O—H group in the infrared absorption spectrum (in thevicinity of 3500 cm⁻¹) using the FT-IR method (Fourier TransformInfrared Spectroscopy). Ion implantation was carried out under thecondition of an acceleration energy of 140 KeV and a dose of 1×10¹⁵atoms/cm².

[0078] It is appreciated that the moisture increases, not only beforeand after the treatment, but even after one day for the organic SOG filmexposed to oxygen plasma. In contrast, the modified SOG film shows noincrease in moisture after the ion implantation. Furthermore, theincrease in moisture is smaller than that of the organic SOG film evenwhen left in the atmosphere of a clean room. This means that themodified SOG film is less hygroscopic than the organic SOG film.

[0079]FIG. 14 shows the results of a pressure cooker test (PCT) carriedout for the purpose of evaluating the moisture permeability of amodified SOG film and an organic SOG film. This PCT is a humidificationtest carried out in a saturated moisture atmosphere at 2 atmosphericpressure and 120° C. in the present embodiment. The integrated intensityof the absorption peak (in the vicinity of 3500 cm⁻¹) of the O—H groupin the organic SOG film was obtained and plotted over the PCT time bymeans of the FT-IR method.

[0080] A specimen (Ar ion implantation: 20 KeV) having only the surfacemodified by ion implantation was prepared and compared with a specimenhaving the film entirely modified (Ar ion implantation: 140 KeV) andwith a specimen that was not modified (organic SOG film: untreated). Thefollowing features were identified.

[0081] i) When an organic SOG film not modified is subjected to the PCT,the absorption intensity in the vicinity of 3500 cm⁻¹ (absorptionassociated with O—H group) exhibited a drastic increase.

[0082] ii) With a modified SOG film, increase in the absorptionintensity in the vicinity of 3500 cm⁻¹ (absorption associated with O—Hgroup) is small. The increase in the specimen in which only the filmsurface is modified is substantially equal to that of the film that isthoroughly modified.

[0083] It is understood from the above results that a layer thatsuppresses moisture permeability can be formed by implanting ions.

[0084] Organic SOG films 3 and 7 are converted into modified SOG films 4and 8, respectively, by introducing impurities by ion implantation intothe organic SOG film, whereby moisture and hydroxyl group included inthe film are reduced and exhibits less hygroscopicity. Also, theadhesion with silicon oxide film 2 adjacent to modified SOG film 4 isimproved. An interlayer insulation film of high reliability can beobtained.

[0085] Second Embodiment

[0086] A method of fabricating a semiconductor device according to asecond embodiment of the present invention will be described hereinafterwith reference to FIGS. 15-20. The first to sixth steps (FIGS. 1-6) ofthe first embodiment are similarly employed in the second embodiment.Therefore, description thereof will not be repeated. Fabrication stepsthereafter will be described. Components corresponding to those of thefirst embodiment have the same reference characters allotted, anddetailed description thereof will not be repeated.

[0087] At the tenth step (refer to FIG. 15), a mask pattern 13 (siliconnitride film mask 13) formed of a silicon nitride film is provided onmodified SOG film 8. Silicon nitride film mask 13 corresponds to thefirst mask pattern of the present invention.

[0088] At the eleventh step (refer to FIG. 16), an organic SOG film 14of 600 nm in thickness is formed on modified SOG film 8 and siliconnitride film mask 13. The composition and fabrication method of organicSOG film 14 are similar to those of organic SOG film 3 alreadydescribed. Organic SOG film 14 corresponds to the third insulation filmof the present invention.

[0089] At the twelfth step (refer to FIG. 17) ions are implanted intoorganic SOG film 14 to form a modified SOG film 15. The composition andfabrication method of modified SOG film 15 are similar to those of thepreviously-described modified SOG film 4. Since organic SOG film 14 hassubstantially a uniform thickness over the entire face of the substrate,the entire organic SOG film 14 is modified substantially uniformly.

[0090] At the thirteenth step (refer to FIG. 18), a striped resistpattern 16 is formed on modified SOG film 15. The opening of resistpattern 16 includes the opening of silicon nitride film mask 13. Thearea of resist pattern 16 is larger than that of silicon nitride filmmask 13. Resist pattern 16 corresponds to the second mask pattern of thepresent invention.

[0091] At the fourteenth step (refer to FIG. 19), anisotropic etching iscarried out with resist pattern 16 as a mask using fluoro carbon gas asetching gas, whereby modified SOG films 15 and 8 are etched. Here,modified SOG film 15 is etched with an opening width identical to thatof resist pattern 16. The etching process of modified SOG film 15 isstopped when arriving at silicon nitride film mask 13, whereby trenches17 a and 17 b are formed in modified SOG film 15. Then, using siliconnitride film mask 13 as a mask, modified SOG film 8 is etched with anopening diameter identical to that of the mask. Contact holes 17 c and17 d are formed communicating with metal interconnection 6 in modifiedSOG film 8.

[0092] By using silicon nitride film mask 13 as an etching stopper,trenches 17 a and 17 b and contact holes 17 c and 17 d can be formed byone etching process. Even when the position of the formed contact holeis deviated from the top face of metal interconnection 6 such as contacthole 17 d due to mask misalignment so that modified SOG film 4 isexposed, contact error will not occur due to reasons similar to thosefor contact hole 9 b.

[0093] At the fifteenth step (refer to FIG. 20), the interior oftrenches 17 a and 17 b and contact holes 17 c and 17 d are cleaned bymeans of sputter etching using inert gas (for example, Ar). Then, a TiNfilm as an adhesion layer and a barrier layer is formed by magnetronsputtering or CVD on modified SOG film 15 including trenches 17 a and 17b and contact holes 17 c and 17 d. A Cu film is formed thereon by CVD orplating. The surface of the Cu film is polished by CMP. Eventually, aninterconnection 18 formed of TiN and Cu is embedded in trenches 17 a and17 b and contact holes 17 c and 17 d.

[0094] Third Embodiment

[0095] A method of fabricating a semiconductor device according to athird embodiment of the present invention will be described hereinafterwith reference to FIGS. 21-26. The first to sixth steps (FIGS. 1-6) ofthe first embodiment are employed in the present third embodiment.Description thereof will not be repeated and fabrication stepsthereafter will be described. Components corresponding to those of thefirst and second embodiments have the same reference charactersallotted, and detailed description thereof will not be repeated.

[0096] At the twentieth step (refer to FIG. 21), a resist pattern 20 isformed on modified SOG film 8 (film thickness is set to 1200 nm). Theopening of resist pattern 20 includes the opening (metal interconnection6) of trench 5. The area thereof is larger than that of trench 5.

[0097] At the twenty-first step (refer to FIG. 22), anisotropic etchingis carried out with resist pattern 20 as a mask using fluoro carbon typegas as the etching gas. Modified SOG film 8 is etched to the thicknessof 600 nm, whereby trenches 8 a and 8 b are formed in modified SOG film8.

[0098] At the twenty-second step (refer to FIG. 23), resist pattern 20is removed, and then a resist pattern 21 is formed on modified SOG film8. Opening 21 a of resist pattern 21 is located within trenches 8 a and8 b.

[0099] At the twenty-third step (refer to FIG. 24), anisotropic etchingwith resist pattern 21 as a mask is carried out using fluoro carbon typegas as the etching gas, whereby modified SOG film 8 is etched.

[0100] At the twenty-fourth step (refer to FIG. 25), trenches 8 a and 8b and contact holes 22 a and 22 b communicating with metalinterconnection 6 are formed in modified SOG film 8 by removing resistpattern 21. Even if a contact hole is formed deviated in position causedby mask misalignment in the formation of resist pattern 22 so thatmodified SOG film 4 is exposed, no contact error will occur by reasonssimilar to those for contact hole 9 b.

[0101] At the twenty-fifth step (refer to FIG. 26), the interior oftrenches 8 a and 8 b and contact holes 22 a and 22 b are cleaned bymeans of sputter etching using an inert gas (for example Ar). Then, aTiN film as an adhesion layer and a barrier layer is formed by magnetronsputtering or CVD on modified SOG film 8 including trenches 8 a and 8 band contact holes 22 a and 22 b. A Cu film is formed thereon by CVD orplating. The surface of the Cu film is polished by CMP. Eventually, aconnection hole interconnection 18 formed of TiN and Cu is embedded incontact holes 22 a and 22 b.

[0102] Fourth Embodiment

[0103] A method of fabricating a semiconductor device according to afourth embodiment of the present invention will be described hereinafterwith reference to FIGS. 27-33. The first to sixth steps (FIGS. 1-6) ofthe first embodiment are employed in the fourth embodiment. Therefore,description thereof will not be repeated. The fabrication stepsthereafter will be described. Components corresponding to those of thesecond embodiment have the same reference characters allotted, anddetailed description thereof will not be repeated.

[0104] At the thirtieth step (refer to FIG. 27), a resist pattern 30 isformed on modified SOG film 8.

[0105] At the thirty-first step (refer to FIG. 28), anisotropic etchingis carried out with resist pattern 30 as a mask, using fluoro carbontype gas as the etching gas. As a result, contact holes 31 a and 31 bcommunicating with metal interconnection 6 are formed in modified SOGfilm 8.

[0106] At the thirty-second step (refer to FIG. 29), resist pattern 30is removed. Then, a resist film 32 is applied on modified SOG film 8including contact holes 31 a and 31 b.

[0107] At the thirty-third step (refer to FIG. 30), resist film 32 ispatterned excluding the area where contact holes 31 a and 31 b areformed using the general exposure technique to form a resist pattern 33on modified SOG film 8. Openings 33 a and 33 b of resist pattern 33include contact holes 31 a and 31 b. The area thereof is greater thanthat of contact holes 31 a and 31 b.

[0108] At the thirty-fourth step (refer to FIG. 31), anisotropic etchingis carried out with resist pattern 33 and resist film 32 remaining incontact holes 31 a and 31 b as a mask, using fluoro carbon type gas asthe etching gas. Modified SOG film 8 is etched to ½ the film thickness.Thus, trenches 8 a and 8 b are formed in modified SOG film 8.

[0109] At the thirty-fifth step (refer to FIG. 32), trenches 8 a and 8 band contact holes 31 a and 3 b communicating with metal interconnection6 are formed in modified SOG film 8 by removing resist pattern 33 andresist film 32. Here, even if the position of a formed contact hole isdeviated from the top face of metal interconnection 6 such as contacthole 31 b to expose modified SOG film 4 due to misalignment in theformation of resist pattern 30, no contact error will occur due toreasons similar to those for contact hole 9 b.

[0110] At the thirty-sixth step (refer to FIG. 33), the interior oftrenches 8 a and 8 b and contact holes 31 a and 31 b are cleaned bymeans of sputter etching using inert gas (for example Ar). Then, a TiNfilm is formed as an adhesion layer and a barrier layer by sputtering orCVD. Then, a Cu film is formed by CVD or plating thereon. The surface ofthe Cu film is polished by CMP. Finally, a connection holeinterconnection 18 formed of TiN and Cu is embedded in trenches 8 a and8 b and contact holes 31 a and 31 b.

[0111] Fifth Embodiment

[0112] Following the steps shown in FIGS. 1-6 and the steps shown inFIGS. 15 and 16, the steps shown in FIGS. 34-39 are carried out in thefifth embodiment. Components corresponding to those of the previousembodiments have the same reference characters allotted, and descriptionthereof will not be repeated.

[0113] At the thirty-seventh step (refer to FIG. 34), a silicon nitridefilm 40 is deposited all over organic SOG film 14.

[0114] At the thirty-eighth step (refer to FIG. 35), impurities areintroduced into organic SOG film 14 by carrying out ion implantationfrom above silicon nitride film 40 to form a modified SOG film 15. Sinceorganic SOG film 14 has substantially a uniform thickness all over theface of the substrate, the entire organic SOG film 14 is modifiedsubstantially uniformly.

[0115] At the thirty-ninth step (refer to FIG. 36), a striped resistpattern 16 is formed on silicon nitride film 40. The opening of resistpattern 16 is located upper than the opening of silicon nitride filmmask 13. The area thereof is greater than that of silicon nitride filmmask 13.

[0116] At the fortieth step (refer to FIG. 37), silicon nitride film 40is patterned using resist pattern 16 as a mask.

[0117] At the forty-first step (refer to FIG. 38), resist pattern 16 isremoved. Then, modified SOG film 15 and modified SOG film 8 are etchedwith the patterned silicon nitride film 40 as a mask. By this etchingprocess, trenches 17 a and 17 b are formed in modified SOG film 15.Contact holes 17 c and 17 d communicating with metal interconnection 6are formed in modified SOG film 8.

[0118] At the forty-second step (refer to FIG. 39), a TiN film is formedas an adhesion layer and a barrier layer by magnetron sputtering or CVDon silicon nitride film 40 including trenches 17 a and 17 b and contactholes 17 c and 17 d. A Cu film is formed thereon by CVD or plating. Thesurface of the Cu film is polished by CMP. Eventually, aninterconnection 18 formed of TiN and Cu is embedded in trenches 17 a and17 b and contact holes 17 c and 17 d.

[0119] The present invention is not limited to the above-describedembodiments. Similar advantages can be achieved by implementation as setforth in the following.

[0120] (1) A fluoro carbon film, polyimide, or polyimide composed withsiloxane can be used instead of the organic SOG film.

[0121] (2) The interconnection can be formed of aluminum, gold, silver,silicide, refractory metal, doped polysilicon, titanium nitride (TiN),titanium tungsten (TiW) or a layered structure thereof, instead of theCu material.

[0122] (3) The TiN serving as an adhesion layer and a barrier layer canbe formed of a layered structure of Ti, TaN, Ta, and the like.Alternatively, Ti, TaN, Ta can be used instead of TiN.

[0123] (4) The modified SOG film is subjected to a heat treatment. Inthis case, the hygroscopicity is further reduced since there are fewerdangling bonds in the modified SOG film. The moisture permeability isalso reduced.

[0124] (5) The composition of the organic SOG film can be substitutedwith that of the inorganic SOG film represented by the aforementionedgeneral formula (1), and implant ions into that inorganic SOG film. Inthis case, the moisture and hydroxyl group included in the inorganic SOGfilm can be reduced.

[0125] (6) Although boron ions are employed as the impurities to beimplanted into the organic SOG film in the above embodiments, any ionmay be used as long as the organic SOG film is eventually modified.Specifically, argon ions, boron ions, nitrogen ions and the like thathave a relatively small mass are suitable. Particularly, boron ions aremost suitable. Sufficient effect can be expected from other ionsenumerated in the following.

[0126] Inert gas ions (such as helium ion, neon ion, krypton ion, xenonion and radon ion) can be used. Since inert gas does not react with theorganic SOG film, there is no probability of adverse influence by ionimplantation.

[0127] Element unitary ions in each group of III b, IV b, V b, VI b andVII b, and compound ions thereof can also be used. Particularly, theelement unitary ions and compound ions of oxygen, aluminum, sulfur,chlorine, gallium, germanium, arsenic, selenium, bromine, antimony,iodine, indium, tin, tellurium, lead, and bismuth can be used.Particularly, metal element ions can suppress the dielectric constant ofthe organic SOG film subjected to ion implantation.

[0128] Also, element unitary ions of the groups IVa, Va and compoundions thereof can be used. Particularly, element unitary ions oftitanium, vanadium, niobium, hafnium, and tantalum, and compound ionsthereof can be used. Since the dielectric constant of oxides of theelements of the groups IVa and Va is high, the dielectric constant ofthe organic SOG film subjected to ion implantation will increase.However, this is of no particular problem in practice except for thecase where an interlayer insulation film of a low dielectric constant isrequired.

[0129] A plurality of the types of the above-described ions can be usedin combination. In this case, a further superior effect can be obtainedby the synergism of each ion.

[0130] (7) In the above-described embodiments, ions are implanted intothe organic SOG films. The present invention is not limited to ions, andatoms, molecules, or particles can be introduced. (In the presentinvention, they are generically referred to as “impurities”).

[0131] (8) Sputtering is not limited to magnetron sputtering. Diodesputtering, radio frequency sputtering, tetrode sputtering and the likecan be employed.

[0132] (9) The sputter etching method can be carried out without usinginert gas. For example, reactive ion beam etching (RIBE: also calledreactive ion milling) using reactive gas (for example, CCl₄, SF₆) can beused.

[0133] (10) As an alternative to the single crystal silicon substrate(semiconductor substrate), a conductive substrate or an insulativesubstrate such as glass can be used. Although the above-describedembodiments show the case where an interconnection is formed on a singlecrystal silicon substrate, the present invention is also applicable to adevice such as a LCD that has the interconnection formed on aninsulative substrate. It is understood that the concept of“semiconductor device” of the present invention includes a device havingan interconnection formed on an insulative substrate.

[0134] Although the present invention has been described and illustratedin detail, it is clearly understood that the same is by way ofillustration and example only and is not to be taken by way oflimitation, the spirit and scope of the present invention being limitedonly by the terms of the appended claims.

What is claimed is:
 1. A fabrication method of a semiconductor devicecomprising the steps of: forming a first insulation layer on asubstrate, introducing impurities into said first insulation layer, andembedding and forming a first conductive layer in said first insulationlayer.
 2. The fabrication method of a semiconductor device according toclaim 1 , wherein said step of forming a first conductive layer includesthe step of embedding the first conductive layer in said firstinsulation layer so as to expose a surface of said first conductivelayer, and said fabrication method further comprising the steps of:forming a second insulation layer on said first insulation layer,forming a contact hole in said second insulation layer, exposing aportion of said first conductive layer, and forming a second conductivelayer in said contact hole, electrically connected to said firstconductive layer.
 3. The fabrication method of a semiconductor deviceaccording to claim 2 , further comprising the step of introducingimpurities into said second insulation layer.
 4. The fabrication methodof a semiconductor device according to claim 2 , comprising, afterformation of said second insulation layer and before formation of saidcontact hole, the steps of: forming a first mask pattern on said secondinsulation layer, forming a third insulation layer on said secondinsulation layer and on said first mask pattern, forming a second maskpattern on said third insulation layer, having an opening larger thansaid first mask pattern, and etching said third insulation layer usingsaid second mask pattern to form a trench in said third insulation layerreaching to said first mask pattern, wherein said step of forming acontact hole includes the step of etching said second insulation layerusing said first mask pattern, and wherein said step of forming a secondconductive layer includes the step of forming a third conductive layerin said trench, electrically connected to said second conductive layer,in addition to formation of said second conductive layer.
 5. Thefabrication method of a semiconductor device according to claim 4 ,further comprising the step of introducing impurities into said thirdinsulation layer.
 6. The fabrication method of a semiconductor deviceaccording to claim 1 , further comprising the step of forming a fourthinsulation layer on said substrate, prior to formation of said firstinsulation layer, wherein said step of introducing impurities into thefirst insulation layer is carried out under a condition where introducedimpurities arrive at an interface between said first insulation layerand said fourth insulation layer.
 7. The fabrication method of asemiconductor device according to claim 1 , wherein said firstinsulation layer includes a silicon oxide film containing at least 1% ofcarbon.
 8. The fabrication method of a semiconductor device according toclaim 2 , wherein said second insulation layer includes a silicon oxidefilm containing at least 1% of carbon.
 9. The fabrication method of asemiconductor device according to claim 4 , wherein said thirdinsulation layer includes a silicon oxide film containing at least 1% ofcarbon.
 10. The fabrication method of a semiconductor device accordingto claim 1 , wherein said first insulation layer includes an inorganicSOG film.
 11. The fabrication method of a semiconductor device accordingto claim 2 , further comprising, after formation of said secondinsulation layer and before formation of said contact hole, the stepsof: forming a third mask pattern on said second insulation layer,etching said second insulation layer using said third mask pattern toselectively reduce thickness of said second insulation layer, andforming a fourth mask pattern on said second insulation layer so as toexpose a portion of the region reduced in thickness, wherein said stepof forming a contact hole includes the step of etching said secondinsulation layer using said fourth mask pattern, and said step offorming a second conductive layer includes the step of forming a thirdconductive layer on said region reduced in thickness, electricallyconnected to said second conductive layer, in addition to formation ofsaid second conductive layer.
 12. The fabrication method of asemiconductor device according to claim 1 , further comprising the stepsof: forming a second insulation layer on said first insulation layer,forming a fifth mask pattern on said second insulation layer, etchingsaid second insulation layer using said fifth mask pattern to form acontact hole in said second insulation layer, exposing a portion of saidfirst conductive layer, after removing said fifth mask pattern, forminga resist film in said contact hole and on said second insulation layer,forming a sixth mask pattern on said contact hole, having an openinglarger than that contact hole, by patterning said resist film on saidsecond insulation layer, etching said second insulation layer using saidsixth mask pattern to selectively reduce thickness of said secondinsulation layer, removing the resist film remaining in said contacthole and said sixth mask pattern, and forming a second conductive layerin said contact hole, electrically connected to said first conductivelayer.
 13. The fabrication method of a semiconductor device according toclaim 2 , further comprising the step of introducing impurities intosaid second insulation layer, prior to forming said contact hole in saidsecond insulation layer.
 14. A semiconductor device comprising: a firstconductive layer having a top face on a first plane, a first insulationlayer into which impurities are introduced, having a top face on asecond plane parallel to said first plane, and a second insulation layerinto which impurities are introduced, having a top face on a third planeparallel to said second plane, and a second conductive layer embedded insaid first insulation layer, having a bottom in contact with the topface of said first conductive layer and a top face located on saidsecond plane, and a third conductive layer embedded in said secondinsulation layer, having a bottom in contact with the top face of saidsecond conductive layer and a top face located on said third plane. 15.The semiconductor device according to claim 14 , wherein said secondconductive layer and said third conductive layer are a single layerformed continuously.
 16. The semiconductor device according to claim 14, wherein said first insulation layer and said second insulation layerare a single layer formed continuously, and said second conductive layerand said third conductive layer are a single layer formed continuously.17. The semiconductor device according to claim 14 , wherein each ofsaid first and second insulation layers includes an SOG film into whichimpurities are introduced by ion implantation.
 18. The semiconductordevice according to claim 17 , wherein each of said first and secondinsulation layers includes a silicon nitride film on said SOG film. 19.The semiconductor device according to claim 14 , wherein said firstconductive layer is embedded in a planarized insulation layer.
 20. Thesemiconductor device according to claim 19 , wherein said insulationlayer includes an SOG film into which impurities are introduced by ionimplantation.